Characteristics and properties of Cr coatings electrodeposited from Cr(III) baths

The effects of bath composition and deposition condition on trivalent chromium electrodeposition were investigated. Corrosion and tribological behavior of the Cr film was also studied and the results were compared to the substrate. According to the results, there was an optimum amount for each one of the bath Cr-2(SO4)(3)center dot 6H(2)O (chromium sulfate) concentration, pH and current density at which the highest current efficiency was obtained. However, the current efficiency was continuously decreased by raising the bath temperature and deposition time. According to hardness evaluations, enhancing temperature, pH and Cr-2(SO4)(3)center dot 6H(2)O concentration of the bath decreased microhardness of the Cr films. XRD and SEM results revealed that all the Cr electrodeposits had an amorphous structure and nodular morphology. Polarization and impedance results showed that the 316 L stainless steel substrate was more corrosion resistant than the optimum Cr coating. Corrosion potential of the substrate was nobler and its corrosion current density was half of the Cr film. However, the wear loss and friction coefficient of the substrate were about 3 and 1.5 times higher than the Cr coating, respectively.